Although seven of the court's 11 justices deemed the measure that says life begins at conception unconstitutional, they were short of the eight votes needed to overturn it.

Reporting from Mexico City — Abortion foes in Mexico scored a victory Wednesday when the Supreme Court narrowly upheld a provision of Baja California's state constitution saying life begins at conception.

Although seven of the court's 11 justices deemed the measure unconstitutional, they were short of the eight votes needed to overturn it.

The court debate carried heightened suspense because two of the tribunal's 11 members have joined since the court's 2008 ruling upholding a Mexico City law allowing access to abortion. As it turned out, one new judge voted to uphold the Baja California measure and the other voted to invalidate it.

Abortion opponents who had been camped outside the Supreme Court building whooped with glee at word of the ruling. In Baja California, Catholic Archbishop Rafael Romo of Tijuana hailed it as "a positive decision."

Advocates for reproductive rights called the close ruling a temporary setback in the country's abortion debate.

"Years ago no one would have thought seven justices would have ruled this way. I think these are slow but sure steps," Regina Tames, director of the pro-choice group GIRE, said in a radio interview.

The court, ruling after three days of debate, next takes up a challenge to a similar anti-abortion law in the central state of San Luis Potosi.

The two cases have been watched as a measure of abortion rights in Mexico, where more than a dozen states have enacted similar laws as a response to a move by Mexico City to legalize abortion in 2007. Outside the capital, abortion is already illegal, except in some circumstances, but it is infrequently prosecuted.

Justices who opposed the measures explicitly granting rights to the unborn said such laws exceed states' authority and endanger women's rights by closing off access to legal abortion, even in cases of rape or when the mother's health is endangered.

"Criminalizing the interruption of a pregnancy in all cases … is disproportionate and unreasonable, while at the same time violating women's dignity and autonomy," said Justice Fernando Franco, who is leading the charge to overturn the state laws.

But several justices said state legislatures were within their rights to write into their local constitutions statements about when life begins.

"There is no human being who wasn't conceived. An embryo dies without the mother dying, evidence of an independent life to which Mexican law has recognized the right of protection since the 19th century," said Justice Salvador Aguirre Anguiano.

The abortion issue has volleyed between local legislatures and courts since Mexico City's assembly voted in 2007 to allow abortions during the first three months of pregnancy.

That law made Mexico City, which is formally treated as a state, the first place in the country allowing legal access to abortion. The Supreme Court upheld the capital's law by an 8-to-3 vote a year later.

But the ruling did not generate abortion rights measures across Mexico, as supporters hoped. Instead, opponents worked to enact constitutional amendments declaring that life begins at conception. Pushed by the conservative National Action Party of President Felipe Calderon and backed by the Catholic Church, measures passed in a rapid succession of legislatures, often with little debate.

To date, 18 of Mexico's 31 states have passed such laws, prompting abortion rights activists to charge that abortion is being criminalized across much of the country. Some critics say the laws clash with federal standards allowing birth-control methods such as intrauterine devices or the "morning after" pill.

Women have been jailed for unlawful abortions in several states, but in some cases freed after challenges reached the Supreme Court.

Baja California's amendment, passed in 2008, establishes a person's right to legal protection "from the moment an individual is conceived." The state's human rights ombudsman filed the legal challenge to the provision.

San Luis Potosi's constitution, like new laws in the remaining 16 states, also says life begins at conception.

Justice Margarita Luna Ramos voted in favor of the Baja California measure, after arguing that just as states have legal authority to allow abortion, they are free to declare that life begins at conception.

But Justice Arturo Zaldivar voted to strike down the measure, saying that sending women, especially the poor, in search of back-alley abortions or even to jail was "profoundly unfair, profoundly immoral and profoundly unconstitutional."